Count (#2084)

* Add files via upload

* Update and rename count_islands.py to count_islands_in_matrix.py

* Update matrix/count_islands_in_matrix.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update matrix/count_islands_in_matrix.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update matrix/count_islands_in_matrix.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Reformat count islands.py

* Indent Python code with 4 spaces, not tabs

* Update count_islands_in_matrix.py

* Add type hints for return values

Co-authored-by: Christian Clauss <cclauss@me.com>

matrix/count_islands_in_matrix.py

@@ -0,0 +1,36 @@
+# An island in matrix is a group of linked areas, all having the same value.
+# This code counts number of islands in a given matrix, with including diagonal
+# connections.
+
+
+class matrix:  # Public class to implement a graph
+    def __init__(self, row: int, col: int, graph: list):
+        self.ROW = row
+        self.COL = col
+        self.graph = graph
+
+    def is_safe(self, i, j, visited) -> bool:
+        return (
+            0 <= i < self.ROW
+            and 0 <= j < self.COL
+            and not visited[i][j]
+            and self.graph[i][j]
+        )
+
+    def diffs(self, i, j, visited):  # Checking all 8 elements surrounding nth element
+        rowNbr = [-1, -1, -1, 0, 0, 1, 1, 1]  # Coordinate order
+        colNbr = [-1, 0, 1, -1, 1, -1, 0, 1]
+        visited[i][j] = True  # Make those cells visited
+        for k in range(8):
+            if self.is_safe(i + rowNbr[k], j + colNbr[k], visited):
+                self.diffs(i + rowNbr[k], j + colNbr[k], visited)
+
+    def count_islands(self) -> int:  # And finally, count all islands.
+        visited = [[False for j in range(self.COL)] for i in range(self.ROW)]
+        count = 0
+        for i in range(self.ROW):
+            for j in range(self.COL):
+                if visited[i][j] is False and self.graph[i][j] == 1:
+                    self.diffs(i, j, visited)
+                    count += 1
+        return count